1. Field of the Invention
The present invention relates to a negative active material for a non-aqueous electrolyte battery, a method of preparing the same, and a non-aqueous electrolyte battery comprising the same, and more particularly to a negative active material of a non-aqueous battery with effective stability, a method of preparing the same, and a non-aqueous battery comprising the same.
2. Description of the Related Art
Rechargeable lithium batteries, which are attractive as power sources for portable electronics, use organic electrolyte, and exhibit twice the discharge capacity of conventional batteries with alkaline aqueous solution electrolyte as well as having a higher energy density.
Positive active materials of rechargeable lithium batteries use lithium and transition metal-included oxides having a structure being capable of intercalating lithium, such as LiCoO2, LiMn2O4, and LiNi1−xCoxO2 (0<x<1).
Negative active materials use carbonaceous materials which may intercalate and deintercalate lithium, such as graphite, e.g., artificial graphite, natural graphite, natural graphite, or hard carbon. A lower discharge voltage to lithium, i.e., −0.2 V of graphite, renders a higher discharge voltage of 3.6 V which provides advantages in energy density, and good reversibility guarantees long cycle life. Owing to these advantages, graphite is widely used as the negative active material. However, graphite has a low density per unit volume of the electrode (nominal density of 2.2 g/cc), which decreases capacity, and graphite easily and undesirably reacts with organic electrolytes at high discharge voltages, causing fires or explosion.
These shortcomings are addressed by developing oxide active materials. Amorphous tin oxides studied by FUJI FILM CO. exhibit a high capacity of 800 mAh/g, but initial irreversible capacity reached approximately 50%. In addition, the discharge voltage of 0.5 V or more and an inherently smooth voltage profile cause difficulty in the use of such materials as negative active materials. In addition, a significant amount of reduction from tin oxide to tin metal occurs, which negates the use of such materials as negative active materials.
Various oxide negative active materials have been taught, e.g., in Japanese Patent Laid-Open No. 2002-216753 (SUMITOMO METAL IND., LTD.) (LiaMgbVOc (0.05≦a≦3, 0.12≦b≦2, 2≦2c-a-2b≦5)), and in Abstract #3B05 of The 43rd Battery Symposium in Japan.
However, studies on oxides used as negative active materials exhibiting satisfactory battery performances are still required.